As wireless communication technology develops, systems that use various kinds of communication schemes coexist. For example, a wireless communication system that uses a Code Division Multiple Access (CDMA) scheme called a 2nd generation technique, a wireless communication system that uses an International Mobile Telecommunication (IMT)-2000 scheme called a 3rd generation technique, and a system that uses an Orthogonal Frequency Division Multiplexing (OFDM) scheme called a 4th generation technique coexist. At this point, the systems that use coexisting different communication schemes provide services using different frequency bands. However, since frequency resources for wireless communication are limited, the frequency resources are not sufficient for coexistence of lots of systems.
Therefore, a Cognitive Radio (CR) technique that uses a temporarily unused frequency band or channel of already allocated frequency bands in use is being studied. That is, even a system that is licensed for a specific frequency band always does not use all relevant frequency bands. Therefore, the CR wireless communication system searches for a channel that is temporarily unused by the licensed system, and then provides a service to user terminals inside a service area via the searched channel. For example, temporarily unused frequency bands of allocated frequency bands may be used for transmitting a TeleVision (TV) signal.
In the case of applying a CR technique in the wireless communication system, for efficient sharing of frequency resources, each base station in charge of respective cells needs to share communication information with other base stations. For this purpose, in the CR wireless communication system, base stations transmit a CBP packet including communication information regarding themselves to neighbor base stations via a synchronized Self-Coexistence Window (SCW) slot, and the neighbor base stations receive the CBP packet, so that the communication information is shared. Here, the SCW slot is located at a predetermined portion of every frame, and the CBP packet includes various information related to a self-coexistence algorithm such as a location of a relevant base station, sensing results, scheduling information, a backup channel, and the like.
As described above, in a CR wireless communication system, base stations share information required for respective cells with one another by transmitting/receiving a CBP packet via an SCW. However, since the SCW has a limited amount of resource, in the case where a plurality of base stations intend to transmit CBP packets, collision of CBP packets occurs. When base stations cannot normally receive CBP packets from neighbor base stations due to collision of CBP packets, a system cannot operate normally. Therefore, for a CR wireless communication system to normally operate, an alternative for transmitting/receiving the CBP packet without collision or an error is required.